1. Field of the Invention
The field of the present invention relates to a stop valve.
2. Description of the Prior Art
From the German Patent DT-Gbm 1,941,145 a stop valve is known in which insert rings laterally adjacent to a stopcock are axially screwed into a bore in a housing, the bore is open at each end, and the insert rings press against the stopcock on turning or twisting sealing rings. This stop valve has the disadvantage that a readjustment of both sealing rings adjacent to the stopcock by means of the insert rings is only possible upon disassembling the stop valve to a considerable extent, i.e., loosening the coupling nuts, and removal of the valve from the piping. This stop valve carries with it the additional risk that flowing fluids, or fluids carrying sediment reach the threaded connection or coupling between the housing and the insert rings and cause a more difficult readjustment or resetting of the sealing rings after some lapse of time, or a more difficult disassembly of the insert rings from the housing.
Additionally, a stop valve is disclosed in U.S. Pat. No. 3,550,902 which differs from the aforedescribed valve in that the housing is formed on one side as an applicance with an inserted sealing ring for the stopcock, and on the other side of the housing contains only a loosely fitted insert ring having a sealing ring, the insert ring being kept in position by an adjacent connecting sleeve, as well as by a coupling nut screwed over the housing and extending over the coupling or connecting sleeve. Although the insert ring is axially displaceable and, therefore, readjustable by tightening the coupling nut without removal of the cock, the stopcock is thereby displaced from the center of the actuating shaft and can no longer be operated in a central position and develops a tendency to jam. A further disadvantage is that the stopcock can only be installed in a position in which the insert ring is disposed on the pressure side of the stop valve. Furthermore the seal installed in the depth of the housing wears out more quickly due to being subjected to a higher pressure as a result of the predetermined insert position, and is additionally difficult to exchange.